diff --git a/sfs/util.py b/sfs/util.py
index 006bf47f..f91c4a6a 100644
--- a/sfs/util.py
+++ b/sfs/util.py
@@ -361,7 +361,7 @@ def db(x, power=False):
 
     """
     with np.errstate(divide='ignore'):
-        return 10 if power else 20 * np.log10(np.abs(x))
+        return (10 if power else 20) * np.log10(np.abs(x))
 
 
 class XyzComponents(np.ndarray):
diff --git a/tests/test_util.py b/tests/test_util.py
index 89ff89d1..d46fd76c 100644
--- a/tests/test_util.py
+++ b/tests/test_util.py
@@ -4,14 +4,15 @@
 import sfs
 
 cart_sph_data = [
-    ((1, 1, 1), (np.pi/4, np.arccos(1/np.sqrt(3)), np.sqrt(3))),
-    ((-1, 1, 1), (np.arctan2(1, -1), np.arccos(1/np.sqrt(3)), np.sqrt(3))),
-    ((1, -1, 1), (-np.pi/4, np.arccos(1/np.sqrt(3)), np.sqrt(3))),
-    ((-1, -1, 1), (np.arctan2(-1, -1), np.arccos(1/np.sqrt(3)), np.sqrt(3))),
-    ((1, 1, -1), (np.pi/4, np.arccos(-1/np.sqrt(3)), np.sqrt(3))),
-    ((-1, 1, -1), (np.arctan2(1, -1), np.arccos(-1/np.sqrt(3)), np.sqrt(3))),
-    ((1, -1, -1), (-np.pi/4, np.arccos(-1/np.sqrt(3)), np.sqrt(3))),
-    ((-1, -1, -1), (np.arctan2(-1, -1), np.arccos(-1/np.sqrt(3)), np.sqrt(3))),
+    ((1, 1, 1), (np.pi / 4, np.arccos(1 / np.sqrt(3)), np.sqrt(3))),
+    ((-1, 1, 1), (np.arctan2(1, -1), np.arccos(1 / np.sqrt(3)), np.sqrt(3))),
+    ((1, -1, 1), (-np.pi / 4, np.arccos(1 / np.sqrt(3)), np.sqrt(3))),
+    ((-1, -1, 1), (np.arctan2(-1, -1), np.arccos(1 / np.sqrt(3)), np.sqrt(3))),
+    ((1, 1, -1), (np.pi / 4, np.arccos(-1 / np.sqrt(3)), np.sqrt(3))),
+    ((-1, 1, -1), (np.arctan2(1, -1), np.arccos(-1 / np.sqrt(3)), np.sqrt(3))),
+    ((1, -1, -1), (-np.pi / 4, np.arccos(-1 / np.sqrt(3)), np.sqrt(3))),
+    ((-1, -1, -1), (np.arctan2(-1, -1),
+                    np.arccos(-1 / np.sqrt(3)), np.sqrt(3))),
 ]
 
 
@@ -27,3 +28,43 @@ def test_sph2cart(coord, polar):
     alpha, beta, r = polar
     b = sfs.util.sph2cart(alpha, beta, r)
     assert_allclose(b, coord)
+
+
+direction_vector_data = [
+    ((np.pi / 4, np.pi / 4), (0.5, 0.5, np.sqrt(2) / 2)),
+    ((3 * np.pi / 4, 3 * np.pi / 4), (-1 / 2, 1 / 2, -np.sqrt(2) / 2)),
+    ((3 * np.pi / 4, -3 * np.pi / 4), (1 / 2, -1 / 2, -np.sqrt(2) / 2)),
+    ((np.pi / 4, -np.pi / 4), (-1 / 2, -1 / 2, np.sqrt(2) / 2)),
+    ((-np.pi / 4, np.pi / 4), (1 / 2, -1 / 2, np.sqrt(2) / 2)),
+    ((-3 * np.pi / 4, 3 * np.pi / 4), (-1 / 2, -1 / 2, -np.sqrt(2) / 2)),
+    ((-3 * np.pi / 4, -3 * np.pi / 4), (1 / 2, 1 / 2, -np.sqrt(2) / 2)),
+    ((-np.pi / 4, -np.pi / 4), (-1 / 2, 1 / 2, np.sqrt(2) / 2)),
+]
+
+
+@pytest.mark.parametrize('input, vector', direction_vector_data)
+def test_direction_vector(input, vector):
+    alpha, beta = input
+    c = sfs.util.direction_vector(alpha, beta)
+    assert_allclose(c, vector)
+
+
+db_data = [
+    (0, -np.inf),
+    (0.5, -3.01029995663981),
+    (1, 0),
+    (2, 3.01029995663981),
+    (10, 10),
+]
+
+
+@pytest.mark.parametrize('linear, power_db', db_data)
+def test_db_amplitude(linear, power_db):
+    d = sfs.util.db(linear)
+    assert_allclose(d, power_db * 2)
+
+
+@pytest.mark.parametrize('linear, power_db', db_data)
+def test_db_power(linear, power_db):
+    d = sfs.util.db(linear, power=True)
+    assert_allclose(d, power_db)